Apoptosis and autophagy are both genetically controlled cellular pathways that are involved in determining cell fate, tissue homeostasis, and development. Despite some clues about molecular links between the two pathways, the interrelationship between apoptosis and autophagy is poorly understood. Previously, we identified the mammalian autophagy protein, Beclin 1, that interacts with cellular anti-apoptotic proteins of the Bcl-2 family. In this grant, we propose to explore the functional significance of Beclin 1-Bcl-2 family member interactions with respect to the regulation of autophagy and apoptosis and the role of these interactions in C. elegans and mouse development. In the first specific aim, we will use yeast, C. elegans genetic and mammalian systems to investigate the hypothesis that Bcl-2 orthologs inhibit Beclin 1 ortholog dependent autophagy. We will evaluate whether such inhibition requires direct protein-protein interactions between Bcl-2 orthologs and Beclin 1 orthologs and whether the mechanism involves disruption of the Beclin 1-Class III PI3K complex-associated PI3 kinase activity. In the second specific aim, we will use C. elegans genetic and mammalian systems to investigate the hypothesis that Beclin 1 orthologs function primarily as survival genes that are required for the anti-apoptotic function of Bcl-2 orthologs. We will test whether the survival effects of Beclin 1 orthologs require protein-protein interactions with Bcl-2 orthologs and we will evaluate possible mechanisms by which Beclin 1 orthologs promote anti-death activity of Bcl-2 orthologs. Together, these studies will define the functional significance of interactions between the Bcl-2 anti-apoptotic proteins and Beclin 1 autophagy proteins. The results obtained are expected to help decipher the evolutionarily conserved interrelationships between apoptosis and autophagy pathways and to have important implications for understanding the normal developmental and the pathophysiological processes in which both apoptosis and autophagy occur.